How can I read the agreement field of a template

Questions
1

Hello,
Can someone tell me how can I read in a script the value stored in the agreement field of a contract?
I can set the value in it, but how can I print it out to the console, to see that the value I am storing in it is correct.

2

I don’t believe there’s any way to do this. As far as I can tell, the only way to examine the text in the agreement clause of a Daml template is by looking at the source code of the template.

3

You can extract the text of the agreement from the contract payload using the agreement function, see in the Prelude:

class HasAgreement t where

Exposes agreement function. Part of the Template constraint.

agreement
: t → Text

The agreement text of a contract

This is an example template and script:

module Main where
import DA.List (head)

import Daml.Script

type AssetId = ContractId Asset

template Asset
  with
    issuer : Party
    owner  : Party
    name   : Text
  where
    ensure name /= ""
    agreement show issuer <> " has issued an asset of name " <> show name <> " for " <> show owner <> " as owner."
    signatory issuer
    observer owner
    choice Give : AssetId
      with
        newOwner : Party
      controller owner
      do create this with
           owner = newOwner

setup : Script ()
setup = script do
-- user_setup_begin
  alice <- allocatePartyWithHint "Alice" (PartyIdHint "Alice")
  bob <- allocatePartyWithHint "Bob" (PartyIdHint "Bob")
  aliceId <- validateUserId "alice"
  bobId <- validateUserId "bob"
  createUser (User aliceId (Some alice)) [CanActAs alice]
  createUser (User bobId (Some bob)) [CanActAs bob]
-- user_setup_end

  aliceTV <- submit alice do
    createCmd Asset with
      issuer = alice
      owner = alice
      name = "TV"

  bobTVid <- submit alice do
    exerciseCmd aliceTV Give with newOwner = bob

  bobTvInstances <- query @Asset bob

  debug $ agreement (head bobTvInstances)._2

See the printed agreement text in the transaction view of the script result:

Transactions: 
  TX 0 1970-01-01T00:00:00Z (Main:36:14)
  #0:0
  │   consumed by: #1:0
  │   referenced by #1:0
  │   disclosed to (since): 'Alice' (0)
  └─> 'Alice' creates Main:Asset
              with
                issuer = 'Alice'; owner = 'Alice'; name = "TV"
  
  TX 1 1970-01-01T00:00:00Z (Main:42:14)
  #1:0
  │   disclosed to (since): 'Alice' (1)
  └─> 'Alice' exercises Give on #0:0 (Main:Asset)
              with
                newOwner = 'Bob'
      children:
      #1:1
      │   disclosed to (since): 'Alice' (1), 'Bob' (1)
      └─> 'Alice' creates Main:Asset
                  with
                    issuer = 'Alice'; owner = 'Bob'; name = "TV"

Active contracts:  #1:1

Return value: {}

Trace: 
  "'Alice' has issued an asset of name \"TV\" for 'Bob' as owner."
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4

Thank you @gyorgybalazsi. I stand corrected.

5

Hi @doron_levi,

As @a_putkov explained, there is no way to access the stored value of the agreement text from within Daml. You can only recompute it with the agreement function, as @gyorgybalazsi suggested. Note that, since Daml is deterministic, you can be sure that the recomputed version is equal to the stored value.

The only way to see the actual value stored is through the ledger API.

However, be aware that the agreement will be deprecated in 2.9, and it will be gone in 3.0, so it is maybe better to not rely on this feature.

2 Likes